Optical mixing with difference frequencies to 552 GHz in ultrafast high electron mobility transistors

The technology of optical mixing in three-terminal devices has been extended, for the first time, to submillimeter-wave frequencies, Using a new generation of 50-nm gate InP-based high electron mobility transistors (HEMT's), optically mixed signals were detected to 552 GHz with a signal-to-noise ratio of approximately 5 dB, A novel harmonic three-wave mixing scheme was used for the detection of the optically generated signals. The technique involved downconversion of the signal in the device by the second harmonic of a gate-injected millimeter-wave local oscillator. Measurements were also done at 212 and 382 GHz to estimate the absolute signal strength and conversion losses. Finally, new interesting features in the bias dependence of the optically mixed signal are reported.